1. Field of the Invention:
The present invention relates to a thermally stable, impact resistant, explosive composition which can be initiated by an exploding bridge wire.
2. Prior Art:
It is well known in the prior art to initiate secondary explosive compositions by means of primary explosives. This method, however, involves the use of materials which are subject to accidental initiation by extraneous sources such as, for example, heat, impact, friction, electrostatic discharge, or the like. These hazards are avoided by performing the initiation of the explosives with exploding wires. Exploding wires initiate the explosive composition in which they are embedded only when the applied voltage has a certain value which is specific for a wire of a certain material having a defined length and a defined diameter.
Initiation by exploding wires makes it possible in the case of primary or secondary explosives to progress beyond point initiation to linear, areal or three-dimensional initiation by means of linear, areal, or three-dimensional arrangements of the ignition chain to obtain certain particular detonation fronts or areas of ignition. Ignition chains of this type consist of alternate pieces of a thick wire and a thin wire of the same or a different length. If an electrical impulse of high voltage is passed through such a chain, the thin pieces of wire undergo an explosive reaction.
The advent of the exploding bridge wire provided a safe and convenient method of introducing a large amount of energy into a detonator, thereby eliminating the need for a primary explosive. Presently available exploding bridge wire detonators usually contain pentaerythritol tetranitrate (PETN) as the explosive material. The use of PETN, however, limits the detonator to use in relatively low temperature environments. When explosive devices are expected to function controllably at elevated temperatures such as from about 250.degree. F. to about 550.degree. F., the explosive material must, of course, be quite stable. The problem this creates is that stable explosives are much more difficult to initiate than their less stable counterparts such as PETN. Some detonators have utilized cyclotrimethylene trinitramine (RDX) as the explosive material which can be used to a temperature level in the range of about 350.degree. F.
It would be desirable to provide an explosive composition which is physically and chemially stable at temperatures above 250.degree. F. which can be intiated with an exploding bridge wire.